Johnny Galecki and girlfriend Kelli Garner have made like the atom and split.
Camps for both actors did not immediately respond to requests for comment.
Galecki, 39, and Garner, 30, first stepped out together in 2012 and were spotted together on several high-profile red carpets, including Sunday's Emmy Awards ceremony and the Screen Actors Guild Awards last year.
Garner also joined Galecki at his costar Kaley Cuoco's New Year's Eve nuptials to tennis player Ryan Sweeting. Cuoco plays the actor's on-screen love interest on their highly-rated CBS sitcom. And it's not the first time Galecki has dated a co-worker: He was also linked to his "Roseanne" costar Sara Gilbert (and taught her a thing or two).
On Monday, the actor, who earlier this month got a big pay bump to $1 million per episode along with a couple of his "Big Bang" costars, made his way down the Emmys red carpet solo.
That all started with the Big Bang! BANG! Follow me on Twitter @NardineSaad